1. Field of the Invention
The present invention relates to the analysis of medical devices, and more particularly to devices for holding medical devices during analysis.
2. Discussion of the Related Art
Controlling the elution properties of an active pharmaceutical ingredient (API) from a polymeric matrix is dependent understanding the distribution of the API within the matrix. The formulation and manufacturing process can alter the distribution of the components. Specifically for drug-coated stents, determining the distribution of the API within the matrix and across the stent will enable better understanding of the API release profile.
MALDI mass spectrometry refers to an instrumental technique that allows for molecular imaging of the surface of a matrix coated sample. MALDI mass spectrometry combined with imaging capability is a technique for analyzing a sample when the sample is moved by a stepping motor in sub micrometer steps (usually 10-100 μm step size) and scanned by a high energy laser source which ionizes the spot of the surface in each step. The generated ions are transmitted into a mass spectrometer that records the mass spectrum. Special data analysis software converts the spectral information into an image map. The main advantage of the technique is that the entire mass range of each stepping spot can be collected. The data analysis software can theoretically generate a molecular image for each discrete m/z value between the lower and upper mass limit of the mass spectrometer. Another possible way to generate data is to collect selective data packages in product ion scan mode to eliminate the possible chemical interferences in the sample.
A critical aspect of MALDI is coating the sample with a matrix that helps to ionize and vaporize the sample. In order to coat the samples, they need to be fixed onto a sample holder. All current sample holder designs are flat surfaces or mostly flat surfaces that can not accommodate medical devices that are several millimeters in diameter. Several attempts were made to attach the stents to the flat or mostly flat surfaces using double sided tapes or acrylate glue to hold the stents. However, these means of fixing the stents was not viable for two reasons. First the glue or tape sometimes released the stent during the application of the matrix. Another issue is theoretically the glue or the tape can cause chemical and spatial interferences. The chemical interferences are due to possible ionization of the chemicals in the glue and tape, and the spatial interferences prevent imaging of the complete length of stents since the glue or taps covers part of the stent.